John Popelish wrote:
If there is a standing wave on a wire, and you have a
tiny current transformer sensor you can slide along the wire, you can
measure the instantaneous current (or the RMS) at any point along the
wire. If the sensor sits at a single point and sees an AC current, you
have no way, from this one measurement, if this current is the result of
a standing wave (two oppositely traveling equal waves adding), or a
single traveling wave, or any combination of traveling waves of
different amplitudes. You know only the net current at that point.

But if one it smart enough to slide the sensor up and down the wire
and note the phase is fixed and unchanging, one knows he is dealing
with a standing wave.

If you add the traveling current waves at each point along the line
and plot the amplitude of the sum (that is, of the total current)
versus position, you see a periodic relationship between the amplitude
and position. It's this relationship which is called a "standing
wave". It's so called because its position relative to the line stays
fixed. It's simply a graph of the total current (the sum of the
traveling waves) vs. position.

And that's all it is - the sum of two traveling waves. A standing wave
has no separate existence of its own. It is an artifact of superposition.
--
73, Cecil http://www.qsl.net/w5dxp